Metal matrix reactive composite projectiles

ABSTRACT

A method of making a projectile, and the resulting projectile, comprising providing a nose, providing a body, and incorporating within the body incendiary materials mixed into a metal binder, the metal binder comprising a metal or non-steel alloy of density greater than approximately 5 g/cm 3  and a melting point of less than approximately 395 degrees C.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable.

COPYRIGHTED MATERIAL

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention (Technical Field)

The present invention relates to incendiary and incendiary initiated explosive projectiles.

2. Description of Related Art

A gun is a device that expels solid projectiles at relatively high velocity by using a propellant. The projectile is fired from the gun through the bore of a hollow tube known as the “barrel”. The diameter of the barrel that fires the projectile is typically designated as its caliber, the dimension of which is measured in inches (but may alternately be measured in millimeters). The term “gun” is often used to generally describe all types of projectile-launching devices, but in military nomenclature it refers only to artillery, which is distinguished by its relatively large caliber and size requiring a specialized supporting structure for firing and transport.

The basic distinction between small arms (including weapons such as revolvers, pistols, submachine guns, carbines, assault rifles, rifles, squad automatic weapons, and light machine guns) and artillery (including weapons such as cannon artillery and rocket artillery) is arbitrary and related to the caliber of the barrel. Small arms are typically regarded as having barrels less than 20 millimeters bore size.

Conventional small arms bullets are often comprised of an inert solid lead core encapsulated in a thin outer jacket (often of copper-based composition). The lead imparts a high density to the bullet core permitting good storage of kinetic energy from the reacting propellant, and the copper jacket makes a reliable seal with the barrel bore while minimizing bullet deformation/breakup during launch. Armor piercing bullets typically employ a core of hard steel or other material of relatively high strength, hardness, and density with a jacket, and are designed to minimize deformation and structural breakup of the projectile upon impact with a target in order to maximize depth of penetration. Other projectiles are available that contain an incendiary charge or an arrangement of incendiary and explosive which are used to impart more energy (i.e. in the form of heat and/or fragmentation) to a target than the kinetic energy associated with the fast-moving bullet.

When considering incendiary projectiles, the initiation of the stored reactive materials is usually caused by impact with a relatively hard target. With incendiary initiated explosive projectiles, the explosive charge is set off by a shock wave from the target impact or from heat generated by ignition of the incendiary powder charge.

Impact of soft targets by HEI (High Explosive Incendiary) or PIE (Pyrotechnically Initiated Explosive) ammunition will typically not impart sufficient initiation energy to the reactive materials contained within the projectile to cause a reaction, resulting in live unconsumed high explosive ammunition littering the battlefield. Fuzing and self destruct devices included in ammunition carrying high explosives to actively force an explosive reaction in these projectiles can be unreliable and add a considerable expense to the cost of the ammunition, as well as consume volume that could otherwise contain reactive materials. Neither the high explosive materials nor the incendiary materials are mechanically structural, and both materials require a supporting structure within the projectile to survive launch and penetration into a target. Furthermore, the very limited package size associated with incendiary/explosive projectile ammunition combined with the relatively low mass densities of the explosive and incendiary charges result in a less attractive destructive capacity than would be possible with a more optimized design.

Ammunition associated with artillery (typically employing high-explosive, bomblet, flechette, armor-piercing, and incendiary projectiles) and mortars (typically employing a high-explosive projectile) is well established. Like the smaller caliber guns, artillery projectiles containing incendiary reactive materials are neither particularly structural nor very mass dense. Hard target penetration is facilitated by using a strong, thick projectile case or a penetrating body within the projectile case, both of which consume volume with inert material and act as a conflicting trade against the deliverable volume of nonstructural reactive material.

BRIEF SUMMARY OF THE INVENTION

The present invention is of a method of making a projectile, and the resulting projectile, comprising: providing a nose; providing a body; and incorporating within the body incendiary materials mixed into a metal binder, the binder comprising a metal or metal alloy of density greater than approximately 5 g/cm³ and a melting point of less than approximately 395 degrees C. In the preferred embodiment, the density is between approximately 7.5 and 10.5 g/cm³. The metal binder comprises bismuth, lead, tin, aluminum, magnesium, titanium, gallium, indium, zinc, or alloys thereof, most preferably 52.2% In/45% Sn/1.8% Zn; 58% Bi/42% Sn; 60% Sn/40% Bi; 95% Bi/5% Sn; 55% Ge/45% Al; 63% Sn/37% Pb; 88.3% Al/11.7% Si; 92.5% Al/7.5% Si; and 95% Al/5% Si; zinc alloy UNS Z33523; zinc alloy UNS Z3841, or commercially pure zinc. The resulting projectile has a compressive strength in excess of approximately 14000 psi. The incendiary materials are flaked, powdered, or crystallized, and may be thermite, including thin film thermite. The resulting projectile is substantially insensitive to ignition if impacting a hard surface at less than 300 ft/s. The incendiary materials within the body and mixed into a metal binder are can be additionally mixed with one or more of metastable intermolecular compounds, hydrides, polymeric materials that release a gas upon thermal decomposition, continuous fibers, chopped fibers, whiskers, filaments, structural preforms, woven fibrous materials, dispersed particulates, and nonwoven fibrous materials.

Objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings:

FIG. 1 is a longitudinal sectional view of a HEI projectile of the invention;

FIG. 2 is a longitudinal sectional view of a PIE projectile of the invention; and

FIG. 3 is a longitudinal cutaway sectional view of a jacketed bullet of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is of a method of manufacturing a projectile and projectiles so manufactured. The method utilizes a low melting point metal binder to retain incendiary materials in a monolithic structure, which thereby introduces attractive structural and target-penetrating controls on the behavior of reactive projectiles fired from a gun.

Currently available small arms incendiary ammunition is typically composed of a low density metal powder fuel mixed with a low density powder oxidizer encapsulated within a steel case and surrounded with a copper jacket. The steel case, copper jacket, and encapsulated materials comprise the projectile and are pressed into a propellant-filled case. The incendiary materials are not mechanically structural, and require a supporting structure (i.e., the case/jacket) for containment, launch survivability, delivery to target, and penetration into a target. The very limited package size associated with incendiary projectiles combined with the relatively low mass densities of the incendiary charge results in a less attractive destructive capacity than would be possible with a more optimized design.

Like small arms incendiary ammunition, larger caliber incendiary ammunition also shares the limitations associated with low density energetics (with corresponding sub-optimal target penetration performance) and reduced deliverable energetic material due to volume consumption by the projectile structure.

Utilization of a low melting point metal binder (LMMB) to retain incendiary materials in a monolithic structure can introduce attractive structural and density controls on the behavior of reactive projectiles fired from a gun. Low melting point metal binders are metals and alloys composed of relatively high density elements such as bismuth, lead, tin, zinc, and indium typically in the range of about 5 to 10.5 g/cm³ (compared to common polymeric binders with densities ˜1.5 g/cm³ and steel alloy densities between 7.5 to 8.5 g/cm³). LMMBs have melting points between approximately 47 and 395 degrees C. LMMBs are, however, mechanically tough and when mixed with flaked, powdered, or crystallized energetic components, have favorable structural properties that can enhance projectile ballistics in comparison to conventional reactive projectiles. Compressive strengths in excess of 14000 psi have been measured with associated selectable ductile and brittle failure modes. Well developed ammunition manufacturing processes used to jacket and case-harden lead-based ammunition can be readily employed to facilitate ease of fielding and also further increase the overall penetration capability of the metal matrix reactive composite projectiles. By using a metal binder to package the energetic materials rather than a polymeric binder (or alternately, no binder at all), the overall projectile density and energetic storage volume can be significantly increased resulting in enhanced target lethality beyond that currently available.

Testing has shown that metal matrix reactive composite projectiles containing thermite materials (including reactive thin film thermite) will produce a considerable self-sustaining heat in a rapid reaction event. Testing has also demonstrated that metal matrix reactive composite projectiles can be tailored to initiate upon impact with targets of variable hardness. Additionally, the minimum ignition velocity and overall reaction sensitivity can also be tailored for the application. These materials are categorized as reactive metals (not explosives), and as such do not require IM compliance and are inherently more insensitive than conventionally used high explosives.

Many of the metallic binders considered have reaction energies comparable to metals such as zinc, iron, molybdenum, and tungsten, burning in oxygen and as such, a given binder may effectively impart a significant afterburning component to the blast further extending the overpressure and thermal energy output. Any metal binder material that is not oxidized by afterburning can be readily distributed into the target, increasing the likelihood of electrical short-circuiting if it is deposited onto electronic components.

Successful implementation of the above approach permits an enhanced tradespace involving kinetic energy capacity, thermal energy capacity, penetration capability, projectile structural survivability, and lethality beyond which is available currently. This concept also serves to aid in addressing the increasingly present insensitive munition requirements imposed on reactive material designs.

The binder material can be formed from any suitable metal or combination of metals and/or alloys. According to one embodiment, the binder material preferably comprises a metal or alloy that when combined with the energetic component (or components), the pressure used to compact and densify the structure is of magnitude below that causing autoignition of the energetic materials. According to a further embodiment, the binder material comprises one or more of: bismuth, lead, tin, aluminum, magnesium, titanium, gallium, indium, zinc, and alloys thereof. By way of non-limiting example, suitable binder alloys include (percentages are by mass): 52.2% In/45% Sn/1.8% Zn; 58% Bi/42% Sn; 60% Sn/40% Bi; 95% Bi/5% Sn; 55% Ge/45% Al; 88.3% Al/11.7% Si; 92.5% Al/7.5% Si; and 95% Al/5% Si; zinc alloy UNS Z33523; zinc alloy UNS Z3841, and commercially pure zinc. In addition, the binder material may optionally include one or more reinforcing elements or additives. Thus, the binder material may optionally include one or more of: an organic material, an inorganic material, a metastable intermolecular compound, and/or a hydride. By way of non-limiting example, one suitable additive could be a polymeric material that releases a gas upon thermal decomposition. The composite can also be reinforced by adding one or more of the following organic and/or inorganic reinforcements: continuous fibers, chopped fibers, whiskers, filaments, a structural preform, a woven fibrous material, a dispersed particulate, or a nonwoven fibrous material. Other suitable reinforcements may be employed.

Applying the metal matrix energetic binder technology of the present invention, monolithic reactive composite projectiles can be produced that are mechanically structural and physically resemble commonly used lead-based projectiles. Well developed ammunition manufacturing processes used to jacket and case hardened lead-based ammunition can be readily employed. Because the metal matrix energetic material is suspended in a structural binder, it offers a taylorable blend of target penetration and chemical energy delivery that is not currently available in incendiary ammunition.

FIG. 1 illustrates an HEI projectile 10 made according to the invention, comprising nose 12 (with optional fuzing), projectile body 14, incendiary materials in a metal binder 16, optional tracer 18, and optional rotating band 20. FIG. 2 illustrates a PIE projectile 30 made according to the invention, comprising jacket 32, optional penetrator body 34, base plug 36, and incendiary materials in a metal binder 38. FIG. 3 illustrates a jacketed bullet 40 according to the invention, comprising jacket 42 (having a nose) and incendiary materials in a metal binder 48.

Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference. 

1. A projectile comprising: a nose; a body; and incendiary materials within said body and mixed into a metal binder, said metal binder comprising a metal or metal alloy of density greater than approximately 5 g/cm³ and a melting point of less than approximately 395 degrees C.
 2. The projectile of claim 1 wherein said density is between approximately 7.5 and 10.5 g/cm³.
 3. The projectile of claim 1 wherein said metal binder comprises a member from the group consisting of bismuth, lead, tin, aluminum, magnesium, titanium, gallium, indium, zinc, and alloys thereof.
 4. The projectile of claim 3 wherein said metal binder comprises a member from the group consisting of 52.2% In/45% Sn/1.8% Zn; 58% Bi/42% Sn; 60% Sn/40% Bi; 95% Bi/5% Sn; 55% Ge/45% Al; 63% Sn/37% Pb; 88.3% Al/11.7% Si; 92.5% Al/7.5% Si; and 95% Al/5% Si; zinc alloy UNS Z33523; zinc alloy UNS Z3841, and commercially pure zinc.
 5. The projectile of claim 1 wherein said projectile has a compressive strength in excess of approximately 14000 psi.
 6. The projectile of claim 1 wherein said incendiary materials are flaked, powdered, or crystallized.
 7. The projectile of claim 1 wherein said incendiary materials comprise thermite.
 8. The projectile of claim 6 wherein said incendiary materials comprise thin film thermite.
 9. The projectile of claim 1 wherein said projectile is substantially insensitive to ignition if impacting a hard surface at less than approximately 300 ft/s.
 10. The projectile of claim 1 wherein said incendiary materials within said body and mixed into a metal binder are additionally mixed with one or more of the group consisting of metastable intermolecular compounds, hydrides, polymeric materials that release a gas upon thermal decomposition, continuous fibers, chopped fibers, whiskers, filaments, structural preforms, woven fibrous materials, dispersed particulates, and nonwoven fibrous materials.
 11. A method of making a projectile, the method comprising the steps of: providing a nose; providing a body; and incorporating within the body incendiary materials mixed into a metal binder, the metal binder comprising a metal or metal alloy of density greater than approximately 5 g/cm³ and a melting point of less than approximately 395 degrees C.
 12. The method of claim 11 wherein the density is between approximately 7.5 and 10.5 g/cm³.
 13. The method of claim 11 wherein the metal binder comprises a member from the group consisting of bismuth, lead, tin, aluminum, magnesium, titanium, gallium, indium, zinc, and alloys thereof.
 14. The method of claim 13 wherein the metal binder comprises a member from the group consisting of 52.2% In/45% Sn/1.8% Zn; 58% Bi/42% Sn; 60% Sn/40% Bi; 95% Bi/5% Sn; 55% Ge/45% Al; 63% Sn/37% Pb; 88.3% Al/11.7% Si; 92.5% Al/7.5% Si; and 95% Al/5% Si; zinc alloy UNS Z33523; zinc alloy UNS Z3841, and commercially pure zinc.
 15. The method of claim 11 wherein the resulting projectile has a compressive strength in excess of approximately 14000 psi.
 16. The method of claim 11 wherein the incendiary materials are flaked, powdered, or crystallized.
 17. The method of claim 11 wherein the incendiary materials comprise thermite.
 18. The method of claim 16 wherein the incendiary materials comprise thin film thermite.
 19. The method of claim 11 wherein the resulting projectile is substantially insensitive to ignition if impacting a hard surface at less than approximately 300 ft/s.
 20. The method of claim 11 wherein the incendiary materials within the body and mixed into a metal binder are additionally mixed with one or more of the group consisting of metastable intermolecular compounds, hydrides, polymeric materials that release a gas upon thermal decomposition, continuous fibers, chopped fibers, whiskers, filaments, structural preforms, woven fibrous materials, dispersed particulates, and nonwoven fibrous materials. 